Lens for vehicle lamps



Feb. 2 1926. 'I 1,571,714

R. N. FALGE ET AL LENS FOR VEHICLE LAMPS Filed May 1. 1922 fzxzsz-rzizz'cuas: Bazaar, 182'; Fla: 5.2:, v IZZ'LBERV M daazsrsazsz;

Patented Feb. 2, 1926.

UNITED STATES PATENT OFFICE.

ROBERT N. FALGE AND WILBER M. JOHNSON, OF CLEVELAND, OHIO, ASSIGNORS TOGENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

LENS FOR VEHICLE LAMZPS.

Application fi led May 1,

To all whom it may concern:

Be it known that we, ROBERT N. FALGE and VVILBER M. J OHNSON, bothresiding at Cleveland, county of Cuyahoga, State of Ohio, have inventedcertain new and useful Improvements in Lenses for Vehicle Lamps, ofwhich the following is a specification.

Our invention relates to lenses for headlamps of automobiles and othervehicles. The object of our invention is to provide a lens which willfurnish a desirable distribution of light without glare and which will,at the same time, dispense with the necessity for extreme accuracy oflocation of the light source.

The variation in position of the light source, ordinarily a concentratedinca-ndes cent lamp filament, which is ordinarily caused by inaccuraciesin the manufacture of the lamp or socket, has considerably less effecton the horizontal or approximately horizontal rays emitted from thereflector than it does on the other rays. When the lamp filament islocated exactly at the focus of the parabolic reflector, the rays willbe all approximately horizontal. However, if the filament is displacedfrom the said focus, certain of the rays will be reflected in up warddirections and others in downward di-' vention has to do with the shapeof the zones and, in fact, is of general application where variation inrefraction is required in the different portions of a lens.

In the drawing, which shows preferred forms, Fi ure 1 is a frontelevation of a lens embodying our invention; Figure 2 is the verticalsection thereof on the line 2-2; Figpre 3 is a horizontal section on theline 33; Figure 4 is a diagrammatlc view showing the direction taken bycertain light rays; Figure 5 is a diagrammatic view showing the spotcast on the road by a headlamp com- 1922. Serial No. 557,672.

prising our invention, and Figure 6 is a front elevation of a.modification.

Referring tothe drawing, the lens 10 is provided with the usual clampingmargin 11. The lens is divided into three zones. The intermediate zone12 is that which is encountered by the substantially horizontal rays, orrays making a small angle with the horizontal, reflected by the usualparabolic reflector. Unless the headlamp is tilted downwardly, it ispreferable to construct this central zone so that the light rays arebent slightly downward in order to ensure the avoidance of glare. Theupper zone 13 and the lower zone 14 are prismatic and of such refractivepower that the beams directed thereby are inclined downwardlysufficiently so that no portion thereof is above the beam directed bythe intermediate zone. As shown in Figures 4 and 5, this results inthese beams intersecting the roadway at points not further from thevehicle than the spot cast by the intermediate beam. The aforesaid zones12, 13 and 14 are preferably providedwith spreading prisms. "Inasmuch asthe beams passing through the upper and lower zones 13 and 1e intersectthe roadway at points closest to the vehicle, the refractive power oftheir spreading prisms is preferably made greater than those of zone 12.The preferred form of. our invention is shown diagrammatically in Figure4 and the spots cast by the respective beams are shown in Figure 5. Thespot 15 is cast by the beam directed by the lowermost zone, the spot 16by the beam directed by the upper: most zone, and the spot 17 by thebeam directed by the intermediate zone. Inasmuch as the spot 15 isclosest to the vehicle it is preferably wider than the others, and tothis end the refractive power of the vertical spreading prisms in thelowermost zone is of greater power than that of the corresponding prismsin the other zones.

The intermediate zone is preferably composed of two sectors, being widerat the periphery of the plate than at the center. The angles of spreadare smaller from points at the periphery than from points nearer thecenter portion of the reflector. This arises from the fact that suchpoints are more distant from the filament making the intercepted anglefrom each of said points to the filament smaller and consequentlycausing the beam reflected from such point to be less divergent. Theintermediate zone can therefore be made wider at the periphery of thelens than at the center as shown. More or less trouble is obviated, asshown in Figure 1, by providing a non-transparent or translucent spot 18at the center of the lens since the rays encountering this portion ofthe lens are most affected in their vertical displacement by variations,in the position of the light source or filament. As a modification, thisportion of the intermediate zone may be made more highly refractingdownwardly than the portions more remote from the center.

In Figure 6 we have shown a modification in which the sectors 19 aretrue mathematical sectors being bounded by radii of the lens circle.Such sector sha ed zones may be adopted generally for uni ormlyrefracting portions of a lens. However, we prefer, in order to have afactor of safety,

to make use of a construction similar to Figure 1. I

Whatwe claim as new and desire to secure by Letters Patent of the UnitedStates, 1s:

1. A lens for vehicle head lampshaving focusing reflectors whichcomprises upper, lower and intermediate zones provided with means forretracting downwardly light transmitted therethrough from the reflector,all portions of said upper and lower zones being of higher refractingpower than said intermediate zone and said intermediate zone beingsymmetrically disposed with reference to the transverse axis of saidlens and being wider-at the periphery of said lens than at the centerthereof.

2. A lens for vehicle head lamps having focusing reflectors whichcomprises upper, lower and intermediate zones provided with means forrefracting downwardly 1i ht transmitted therethrough from the re ector,all portions of said upper and lower zones being ofhigher retractingpower than said intermediate zone, .said intermediate zone beingsymmetrically disposed with reference to the transverse axis of saidlens and being wider at the periphery of said ROBERT N. 'FALGE. \VILBERM. JOHNSON.

